The invention relates to a scintillation camera which calibrates the effect of non-linearity inherent to a radiation detecting device thereof to obtain a correct measurement of a radiation position.
As is well known, radiation such as gamma rays is generally measured by using a scintillation camera. In usual gamma rays detection, the gamma rays radiated from a radiation source, for example, the radioisotope injected into a human body or the like are detected by a scintillator such as NaI(T1). The gamma rays detected are converted into a plurality of light quanta to a measurable extent. The light quanta is guided onto photo-multiplier tubes (PMT) on a plane. The outputs of the photo-multiplier tubes are applied to a position calculation circuit where the position of the gamma rays source is calculated. Additionally, the outputs are applied to a pulse height analyzer (PHA) where it is checked to see whether the energy of the outputs is within a given range or not. If the energy falls within the range, the oscilloscope displays its position as a glint spot. Generally, a radiation detecting device including the scintillator, the position calculating circuit and PHA suffers from non-linearity in its characteristic. For this, a preamplifier having the non-linearity so as to compensate for the above-mentioned non-linearity is used in an Anger type scintillation camera having a resistor matrix. However, the causes of the non-linearity are uneven characteristics of the PMT's and aging of the circuit components in addition to the non-linearity inherently produced in manufacturing. The non-linearity due to such causes brings about errors of the measuring data, resulting possibly in erroneous diagnosis.
Another conventional method corrects the non-linear effects for each unit area. However, in this method, there occurs superposition or separation of unit areas so that it is difficult to obtain a stable and correct correction.